Thin-film transistor liquid crystal displays (TFT-LCDs) have become mainstream products in the display field. The basic structure of a TFT-LCD includes an array substrate and an opposing substrate which are arranged opposite to each other, and a liquid crystal layer disposed between them. Generally, thin-film transistors (TFTs) arranged in a matrix are disposed on the array substrate, and a color filter (CF) layer is disposed on the opposing substrate. In this case, the opposing substrate is also referred to as a CF substrate.
In the manufacturing process of the array substrate and the CF substrate of the TFT-LCD, masks are needed in patterning processes. For instance, in the process of manufacturing the array substrate, one mask is required for forming a gate metal layer (e.g., including gate lines and gate electrodes), and another mask is required for forming a transparent electrode layer (e.g., including pixel electrodes). For instance, masks are required for forming the CF layer on the CF substrate.
For instance, the patterning method employing a mask may comprise the following steps: coating photoresist on a film; aligning the mask and the film; irradiating the mask with a light source, whereby the photoresist on the film can sense light passing through the mask; and subsequently, forming a required pattern of the film after developing and etching.
Photoresist includes negative photoresist and positive photoresist. Photoresist converted into an insoluble material after light irradiation is referred to as negative photoresist. In contrast, photoresist which is insoluble in some solvent but converted into a soluble material after light irradiation is referred to as positive photoresist.
In general, a mask is manufactured by forming pattern areas on a substrate such as plastics or glass, so the mask includes a pattern area and a non-pattern area. As for negative photoresist, light emitted by a light source can run through the pattern area of the mask and the light cannot run through the non-pattern area of the mask, so the portion of the negative photoresist corresponding to the pattern area of the mask is exposed and retained in the development process, and the portion of the photoresist corresponding to the non-pattern area is not exposed and removed in the development process. Similarly, as for positive photoresist, the light emitted by the light source cannot run through the pattern area of the mask and the light can run through the non-pattern area of the mask, so the portion of the photoresist corresponding to the pattern area of the mask is not exposed and retained in the development process, and the portion of the photoresist corresponding to the non-pattern area is exposed and removed in the development process.